PRE-2016瓦尔格林: 使用 < iostream > 的普通程序仍然可以访问内存
编辑: 我已经投票结束了，现在这是不正确的。
2016年3月，瓦尔恩获得了一个选项“-run-cxx-freeres = < yes | no >”(默认为 yes)。这将调用一个 libstdc + + 函数来释放用于 iostream 之类事物的一次性分配。如果您使用的是2016年之后的瓦尔格林和 libstdc + + ，那么您将获得
==9356== HEAP SUMMARY:
==9356== in use at exit: 0 bytes in 0 blocks
==9356== total heap usage: 1 allocs, 1 frees, 72,704 bytes allocated
==9356==
==9356== All heap blocks were freed -- no leaks are possible
原文:
以下面这些琐碎的程序为例:
#include <iostream>
int main() {
return 0;
}
如果我运行这个使用瓦尔格林，我被告知，有 72,704 bytes in 1 blocks是 still reachable。关于是否需要担心仍然可以到达的警告，已经进行了广泛的讨论——我不关心这个。我只是想了解，当标准库头 包括的任何对象都没有在程序本身中分配时，它是如何简单地导致仍然可到达的警告的。
以下是完整的 valgrind输出:
$ valgrind --leak-check=full --track-origins=yes --show-reachable=yes ./ValgrindTest
==27671== Memcheck, a memory error detector
==27671== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==27671== Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info
==27671== Command: ./ValgrindTest
==27671==
==27671==
==27671== HEAP SUMMARY:
==27671== in use at exit: 72,704 bytes in 1 blocks
==27671== total heap usage: 1 allocs, 0 frees, 72,704 bytes allocated
==27671==
==27671== 72,704 bytes in 1 blocks are still reachable in loss record 1 of 1
==27671== at 0x4C2AB9D: malloc (vg_replace_malloc.c:296)
==27671== by 0x4EC060F: ??? (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.21)
==27671== by 0x400F305: call_init.part.0 (dl-init.c:85)
==27671== by 0x400F3DE: call_init (dl-init.c:52)
==27671== by 0x400F3DE: _dl_init (dl-init.c:134)
==27671== by 0x40016E9: ??? (in /lib/x86_64-linux-gnu/ld-2.15.so)
==27671==
==27671== LEAK SUMMARY:
==27671== definitely lost: 0 bytes in 0 blocks
==27671== indirectly lost: 0 bytes in 0 blocks
==27671== possibly lost: 0 bytes in 0 blocks
==27671== still reachable: 72,704 bytes in 1 blocks
==27671== suppressed: 0 bytes in 0 blocks
==27671==
==27671== For counts of detected and suppressed errors, rerun with: -v
==27671== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
还有一个对象转储:
$ objdump -d ValgrindTest
ValgrindTest: file format elf64-x86-64
Disassembly of section .init:
0000000000400718 <_init>:
400718: 48 83 ec 08 sub $0x8,%rsp
40071c: e8 8b 00 00 00 callq 4007ac <call_gmon_start>
400721: 48 83 c4 08 add $0x8,%rsp
400725: c3 retq
Disassembly of section .plt:
0000000000400730 <_ZNSt8ios_base4InitC1Ev@plt-0x10>:
400730: ff 35 ba 08 20 00 pushq 0x2008ba(%rip) # 600ff0 <_GLOBAL_OFFSET_TABLE_+0x8>
400736: ff 25 bc 08 20 00 jmpq *0x2008bc(%rip) # 600ff8 <_GLOBAL_OFFSET_TABLE_+0x10>
40073c: 0f 1f 40 00 nopl 0x0(%rax)
0000000000400740 <_ZNSt8ios_base4InitC1Ev@plt>:
400740: ff 25 ba 08 20 00 jmpq *0x2008ba(%rip) # 601000 <_GLOBAL_OFFSET_TABLE_+0x18>
400746: 68 00 00 00 00 pushq $0x0
40074b: e9 e0 ff ff ff jmpq 400730 <_init+0x18>
0000000000400750 <__libc_start_main@plt>:
400750: ff 25 b2 08 20 00 jmpq *0x2008b2(%rip) # 601008 <_GLOBAL_OFFSET_TABLE_+0x20>
400756: 68 01 00 00 00 pushq $0x1
40075b: e9 d0 ff ff ff jmpq 400730 <_init+0x18>
0000000000400760 <__cxa_atexit@plt>:
400760: ff 25 aa 08 20 00 jmpq *0x2008aa(%rip) # 601010 <_GLOBAL_OFFSET_TABLE_+0x28>
400766: 68 02 00 00 00 pushq $0x2
40076b: e9 c0 ff ff ff jmpq 400730 <_init+0x18>
0000000000400770 <_ZNSt8ios_base4InitD1Ev@plt>:
400770: ff 25 a2 08 20 00 jmpq *0x2008a2(%rip) # 601018 <_GLOBAL_OFFSET_TABLE_+0x30>
400776: 68 03 00 00 00 pushq $0x3
40077b: e9 b0 ff ff ff jmpq 400730 <_init+0x18>
Disassembly of section .text:
0000000000400780 <_start>:
400780: 31 ed xor %ebp,%ebp
400782: 49 89 d1 mov %rdx,%r9
400785: 5e pop %rsi
400786: 48 89 e2 mov %rsp,%rdx
400789: 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
40078d: 50 push %rax
40078e: 54 push %rsp
40078f: 49 c7 c0 80 09 40 00 mov $0x400980,%r8
400796: 48 c7 c1 f0 08 40 00 mov $0x4008f0,%rcx
40079d: 48 c7 c7 90 08 40 00 mov $0x400890,%rdi
4007a4: e8 a7 ff ff ff callq 400750 <__libc_start_main@plt>
4007a9: f4 hlt
4007aa: 90 nop
4007ab: 90 nop
00000000004007ac <call_gmon_start>:
4007ac: 48 83 ec 08 sub $0x8,%rsp
4007b0: 48 8b 05 29 08 20 00 mov 0x200829(%rip),%rax # 600fe0 <_DYNAMIC+0x1f0>
4007b7: 48 85 c0 test %rax,%rax
4007ba: 74 02 je 4007be <call_gmon_start+0x12>
4007bc: ff d0 callq *%rax
4007be: 48 83 c4 08 add $0x8,%rsp
4007c2: c3 retq
4007c3: 90 nop
4007c4: 90 nop
4007c5: 90 nop
4007c6: 90 nop
4007c7: 90 nop
4007c8: 90 nop
4007c9: 90 nop
4007ca: 90 nop
4007cb: 90 nop
4007cc: 90 nop
4007cd: 90 nop
4007ce: 90 nop
4007cf: 90 nop
00000000004007d0 <deregister_tm_clones>:
4007d0: b8 37 10 60 00 mov $0x601037,%eax
4007d5: 55 push %rbp
4007d6: 48 2d 30 10 60 00 sub $0x601030,%rax
4007dc: 48 83 f8 0e cmp $0xe,%rax
4007e0: 48 89 e5 mov %rsp,%rbp
4007e3: 77 02 ja 4007e7 <deregister_tm_clones+0x17>
4007e5: 5d pop %rbp
4007e6: c3 retq
4007e7: b8 00 00 00 00 mov $0x0,%eax
4007ec: 48 85 c0 test %rax,%rax
4007ef: 74 f4 je 4007e5 <deregister_tm_clones+0x15>
4007f1: 5d pop %rbp
4007f2: bf 30 10 60 00 mov $0x601030,%edi
4007f7: ff e0 jmpq *%rax
4007f9: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
0000000000400800 <register_tm_clones>:
400800: b8 30 10 60 00 mov $0x601030,%eax
400805: 55 push %rbp
400806: 48 2d 30 10 60 00 sub $0x601030,%rax
40080c: 48 c1 f8 03 sar $0x3,%rax
400810: 48 89 e5 mov %rsp,%rbp
400813: 48 89 c2 mov %rax,%rdx
400816: 48 c1 ea 3f shr $0x3f,%rdx
40081a: 48 01 d0 add %rdx,%rax
40081d: 48 d1 f8 sar %rax
400820: 75 02 jne 400824 <register_tm_clones+0x24>
400822: 5d pop %rbp
400823: c3 retq
400824: ba 00 00 00 00 mov $0x0,%edx
400829: 48 85 d2 test %rdx,%rdx
40082c: 74 f4 je 400822 <register_tm_clones+0x22>
40082e: 5d pop %rbp
40082f: 48 89 c6 mov %rax,%rsi
400832: bf 30 10 60 00 mov $0x601030,%edi
400837: ff e2 jmpq *%rdx
400839: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
0000000000400840 <__do_global_dtors_aux>:
400840: 80 3d e9 07 20 00 00 cmpb $0x0,0x2007e9(%rip) # 601030 <__bss_start>
400847: 75 11 jne 40085a <__do_global_dtors_aux+0x1a>
400849: 55 push %rbp
40084a: 48 89 e5 mov %rsp,%rbp
40084d: e8 7e ff ff ff callq 4007d0 <deregister_tm_clones>
400852: 5d pop %rbp
400853: c6 05 d6 07 20 00 01 movb $0x1,0x2007d6(%rip) # 601030 <__bss_start>
40085a: f3 c3 repz retq
40085c: 0f 1f 40 00 nopl 0x0(%rax)
0000000000400860 <frame_dummy>:
400860: 48 83 3d 80 05 20 00 cmpq $0x0,0x200580(%rip) # 600de8 <__JCR_END__>
400867: 00
400868: 74 1e je 400888 <frame_dummy+0x28>
40086a: b8 00 00 00 00 mov $0x0,%eax
40086f: 48 85 c0 test %rax,%rax
400872: 74 14 je 400888 <frame_dummy+0x28>
400874: 55 push %rbp
400875: bf e8 0d 60 00 mov $0x600de8,%edi
40087a: 48 89 e5 mov %rsp,%rbp
40087d: ff d0 callq *%rax
40087f: 5d pop %rbp
400880: e9 7b ff ff ff jmpq 400800 <register_tm_clones>
400885: 0f 1f 00 nopl (%rax)
400888: e9 73 ff ff ff jmpq 400800 <register_tm_clones>
40088d: 90 nop
40088e: 90 nop
40088f: 90 nop
0000000000400890 <main>:
400890: 55 push %rbp
400891: 48 89 e5 mov %rsp,%rbp
400894: b8 00 00 00 00 mov $0x0,%eax
400899: 5d pop %rbp
40089a: c3 retq
000000000040089b <_Z41__static_initialization_and_destruction_0ii>:
40089b: 55 push %rbp
40089c: 48 89 e5 mov %rsp,%rbp
40089f: 48 83 ec 10 sub $0x10,%rsp
4008a3: 89 7d fc mov %edi,-0x4(%rbp)
4008a6: 89 75 f8 mov %esi,-0x8(%rbp)
4008a9: 83 7d fc 01 cmpl $0x1,-0x4(%rbp)
4008ad: 75 27 jne 4008d6 <_Z41__static_initialization_and_destruction_0ii+0x3b>
4008af: 81 7d f8 ff ff 00 00 cmpl $0xffff,-0x8(%rbp)
4008b6: 75 1e jne 4008d6 <_Z41__static_initialization_and_destruction_0ii+0x3b>
4008b8: bf 34 10 60 00 mov $0x601034,%edi
4008bd: e8 7e fe ff ff callq 400740 <_ZNSt8ios_base4InitC1Ev@plt>
4008c2: ba 28 10 60 00 mov $0x601028,%edx
4008c7: be 34 10 60 00 mov $0x601034,%esi
4008cc: bf 70 07 40 00 mov $0x400770,%edi
4008d1: e8 8a fe ff ff callq 400760 <__cxa_atexit@plt>
4008d6: c9 leaveq
4008d7: c3 retq
00000000004008d8 <_GLOBAL__sub_I_main>:
4008d8: 55 push %rbp
4008d9: 48 89 e5 mov %rsp,%rbp
4008dc: be ff ff 00 00 mov $0xffff,%esi
4008e1: bf 01 00 00 00 mov $0x1,%edi
4008e6: e8 b0 ff ff ff callq 40089b <_Z41__static_initialization_and_destruction_0ii>
4008eb: 5d pop %rbp
4008ec: c3 retq
4008ed: 90 nop
4008ee: 90 nop
4008ef: 90 nop
00000000004008f0 <__libc_csu_init>:
4008f0: 48 89 6c 24 d8 mov %rbp,-0x28(%rsp)
4008f5: 4c 89 64 24 e0 mov %r12,-0x20(%rsp)
4008fa: 48 8d 2d df 04 20 00 lea 0x2004df(%rip),%rbp # 600de0 <__init_array_end>
400901: 4c 8d 25 c8 04 20 00 lea 0x2004c8(%rip),%r12 # 600dd0 <__frame_dummy_init_array_entry>
400908: 4c 89 6c 24 e8 mov %r13,-0x18(%rsp)
40090d: 4c 89 74 24 f0 mov %r14,-0x10(%rsp)
400912: 4c 89 7c 24 f8 mov %r15,-0x8(%rsp)
400917: 48 89 5c 24 d0 mov %rbx,-0x30(%rsp)
40091c: 48 83 ec 38 sub $0x38,%rsp
400920: 4c 29 e5 sub %r12,%rbp
400923: 41 89 fd mov %edi,%r13d
400926: 49 89 f6 mov %rsi,%r14
400929: 48 c1 fd 03 sar $0x3,%rbp
40092d: 49 89 d7 mov %rdx,%r15
400930: e8 e3 fd ff ff callq 400718 <_init>
400935: 48 85 ed test %rbp,%rbp
400938: 74 1c je 400956 <__libc_csu_init+0x66>
40093a: 31 db xor %ebx,%ebx
40093c: 0f 1f 40 00 nopl 0x0(%rax)
400940: 4c 89 fa mov %r15,%rdx
400943: 4c 89 f6 mov %r14,%rsi
400946: 44 89 ef mov %r13d,%edi
400949: 41 ff 14 dc callq *(%r12,%rbx,8)
40094d: 48 83 c3 01 add $0x1,%rbx
400951: 48 39 eb cmp %rbp,%rbx
400954: 75 ea jne 400940 <__libc_csu_init+0x50>
400956: 48 8b 5c 24 08 mov 0x8(%rsp),%rbx
40095b: 48 8b 6c 24 10 mov 0x10(%rsp),%rbp
400960: 4c 8b 64 24 18 mov 0x18(%rsp),%r12
400965: 4c 8b 6c 24 20 mov 0x20(%rsp),%r13
40096a: 4c 8b 74 24 28 mov 0x28(%rsp),%r14
40096f: 4c 8b 7c 24 30 mov 0x30(%rsp),%r15
400974: 48 83 c4 38 add $0x38,%rsp
400978: c3 retq
400979: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
0000000000400980 <__libc_csu_fini>:
400980: f3 c3 repz retq
400982: 90 nop
400983: 90 nop
Disassembly of section .fini:
0000000000400984 <_fini>:
400984: 48 83 ec 08 sub $0x8,%rsp
400988: 48 83 c4 08 add $0x8,%rsp
40098c: c3 retq
为了完整起见，我使用:
Ubuntu: 12.04
瓦尔格林: 3.10.1 < strike > 3.7.0
G + + : 4.8.1
注意: 这种情况不会发生在我包含其他报头的时候，比如 <fstream>或者 <cmath>。
最佳答案